US debates dose of Covid-19 vaccine for children

Some experts suggest increasing the dose of the Pfizer vaccine in children aged 5 to 11, but others say it is not necessary.

For American parents, especially those with young children, the past few months have been a time of uncertainty and anxiety.

In early February, the Food and Drug Administration (FDA) said that Pfizer’s Covid-19 vaccine was not effective enough for the youngest group of children (age 5 and under). Soon after, scientists continued to announce that the vaccine had limited effectiveness when preventing Omicron mutation in the group of 5 to 11 years old.

On March 10, based on these data, Dr. Joseph A. Ladapo, Florida Surgeon General, declared healthy children, without underlying diseases, do not need vaccination. The advice was considered “extremely disturbing” by Jen Psaki, the White House Press Secretary.

To meet the regulator’s criteria, pharmaceutical companies such as Pfizer and Moderna both plan to report the complete results of their clinical trials in the near future. If positive, officials plan to allow vaccination in children from April.

Currently, about 18 million American children under the age of 5 are not eligible for immunization. Scientists at both Pfizer and Moderna are racing to find the optimal dose that’s effective enough to protect babies in the long-term, but not so strong that it causes worrisome side effects, such as a high fever. .

Philip Krause, a former senior manager of vaccines at the FDA, said the agency spent a lot of time deliberating about the safety of the Moderna vaccine in people under the age of 18.

“The question is always: What dose is enough to protect children? We can’t measure the actual incidence of myocarditis because it’s so rare. But you can ask: When to reduce the dose (to vaccines are safe enough, with few side effects), how much immunity do we have to accept? Will that have any effect?”, he said.

Phoebee Curtis, 9, is vaccinated against Covid-19 in Albuquerque, USA. Photo: NY Times

Moderna chooses two injections. The dosage for adolescents 12 to 17 years of age is the same as for adults: 100 micrograms. Children from 6 to 11 years old are given a dose of 50 micrograms. The dose of 25 micrograms is for children under 6 years of age.

Meanwhile, Pfizer offers three injections for children under 5 years old, with a dose of 3 micrograms. Children 5 to 11 years of age get two doses of 10 micrograms each, one-third of what adults and adolescents do.

Amy Rose, a spokeswoman for Pfizer, said that after thorough research, the company chose the “safest and most tolerable” dosage for young children. They hope the three-dose regimen strongly protects children under 5 years of age.

Ofer Levy, a pediatric specialist at Harvard Medical School and a member of the FDA’s independent vaccine advisory committee, said that Pfizer choose the dosage too low for children from 5 to 11 years old. This is likely the cause of the reduced effectiveness of the vaccine in this age group. Accordingly, a recent study by the Centers for Disease Control and Prevention (CDC) found that the effectiveness of Pfizer vaccine in preventing symptoms in children aged 5 to 11 years on average was significantly reduced. To date, this is still the only pharmaceutical company licensed to vaccinate children in this age group.

Moderna applied for a license last year, but the FDA delayed approval because of concerns about the risk of myocarditis. However, some studies show that Moderna maintains protection longer than Pfizer. According to early results, the company’s 50 microgram dose promotes a “strong immune response” in children aged 6 to 11, increasing overall antibody levels.

Because of concerns about myocarditis, CDC encourages adolescents 12 years of age and older, especially men, to increase the interval between two doses of the vaccine to eight weeks.

Dr. Walid F. Gellad, a specialist in pharmaceutical safety, University of Pittsburgh, commented There are not enough data to conclude a high dose of Moderna increases the risk of heart inflammation in young children. Dr Paul Burton, Medical Director of Moderna, cites British research showing that myocarditis is rare, often presenting as mild in people vaccinated with Pfizer and Moderna.

Yvonne Maldonado, a professor of pediatric infectious diseases at Stanford University and principal investigator of the Pfizer trial, said the complete data from both companies will provide insight into vaccine effectiveness for children. .

Thuc Linh (According to NY Times)


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